We propose continuation of funding to complete a biomechanical evaluation of patients with disabling knee joint disease before and after total knee arthroplasty. The objectives of this extension are: 1) to complete the number of patients previously proposed, and 2) to perform objective analysis of the completed patient data to answer a series of specific clinical and biomechanical questions. We have studied 200 preop patients, 143 of whom have returned for one-year postop evaluation. It is essential for us to complete the study of a larger number of postoperative patients for different study periods because: 1) there has been a drastic change in the types of prostheses used in the last two years and the number of each type of prosthesis must be kept at a significant level, and 2) the clinical results have shown that the functional status of total knee patients is not stabilized at one year and follow-up study beyond this period must be conducted. The goniometric method with computerized data collection and reduction capabilities will be utilized. Based on a discriminative analysis technique, the eight most significant gait parameters were used to establish a performance index to grade the gait quality of total knee patients. Two additional methods based on waveform analysis and phase relationship will be applied to differentiate refined gait variations. These results will be presented on a graphic terminal for visual inspection before hard copy is made as a permanent record. A gait evaluation summary has been developed to report to the surgeons the functional status of their patients.